Melasma or chloasma is a common pigmentary condition that affects primarily women in their reproductive years. Dark, mottled (hyperpigmented) patches appear on the face and neck, especially on the cheeks and forehead. Melasma is usually triggered by hormonal activity that is the result of pregnancy or birth control pills. Thus, the condition is known as the “mask of pregnancy”. The condition occurs when excess melanin is deposited in the cells of the epidermis and dermis. Melasma can persist for long periods of time and often recurs with subsequent pregnancies. The condition is less common among men, who account for about 10% of all cases.
Standard therapy involves depigmenting, or bleaching, the affected areas of the skin, the use of sunscreens, and avoidance of sunlight. Hydroquinone is the most popular topical depigmenting agent. Concentrations of 5%-10% hydroquinone are very effective, but can be irritating. The chemical stability of hydroquinone formulations is important because hydroquinone is easily oxidized and loses potency. The most commonly used agent usually involves a 16- to 20-week course of therapy, and some therapies can take longer. Tretinoin (Retin-A) is another widely used therapy for melasma.
Nevertheless, there remains a need in the art for a therapeutic approach that would contain several medicines for the treatment of melasma in a single composition. Moreover, it would be useful to have a therapeutic carrier, such as a cream, that would facilitate the penetration of the medicaments into the skin.
U.S. Pat. No. 5,538,737 discloses a method of making a water-in-oil emulsion containing a pharmaceutically acceptable salt of an H2-antagonist. The steps include dissolving the pharmaceutically acceptable salt in an aqueous medium to form a water portion; combining the water portion with an oil portion, comprising an edible oil comprising an ester or mixed ester of glycerol and an emulsifying agent to form a water portion and oil portion matrix; then emulsifying the matrix to form the water-in-oil emulsion.
U.S. Pat. No. 5,656,672 discloses a process for preparing a water-in-oil emulsion with retinal as the active ingredient. The emulsion contains an oil phase including at least one organic solvent for retinal (such as aliphatic fatty alcohols) and optional lipophilic additives; an aqueous phase containing water and optional hydrophilic additives; and an agent for emulsifying the aqueous phase in the oil phase. The oil phase and the aqueous phase are independently prepared, and the aqueous phase is incorporated into the oil phase, with subsequent addition of a phase-containing retinol and its solvent.
U.S. Pat. No. 5,660,837 discloses a process for the preparation of a pharmaceutical formulation in the form of an oil-in-water emulsion. The steps of the process include of adding the emulsion-stabilizing surface active drug and an optimal conventional surfactant to a two-phase, oil-water system at room temperature; allowing the emulsion-stabilizing surface active drug to equilibrate at an interface; adding an agent giving isotonicity to the final formulation; and homogenizing by high pressure technique.
U.S. Pat. No. 5,976,555 discloses skin care compositions. An oil-in-water emulsion base contains retinoids; cetearyl alcohol and cetearyl glucoside or a mixture of a polyethylene glycol ethers of stearyl alcohol; cetyl alcohol, stearyl alcohol and mixtures thereof; a light, dry absorbable oil; and substantive, emollient oils or waxes.
U.S. Pat. No. 6,080,393 discloses a skin care composition comprising an oil-in-water emulsion with a therapeutically effective amount of a retinoid; wherein the oil phase comprising one or more oils, and an effective amount of at least one oil-soluble antioxidant; and wherein the composition comprises a corticosteroid.
Nevertheless, there remains a need in the art for a method of making a smoother cream base for the application of therapeutic agents for the treatment of melasma, which will facilitate the penetration of the medicaments into the skin.